How a simple yet efficient artificial heart could replace a failing natural one.

Nearly 4,000 people in the US are waiting for heart transplants. And on average, it takes about six months to get one, during which time some patients will die.

So researchers have been trying for decades to make an artificial heart that can be permanently implanted. But building one that imitates a real heart over a long period of time without breaking or causing infections or blood clots is incredibly difficult. One problem is that the more parts there are, the more things could go wrong.